Shock waves, i.e. mechanical waves sometimes also named “acoustic”, are presently used in different ways for therapeutic treatment. Shock wave lithotripsy is especially important and has been the starting point of the development in a historical sense, namely the disintegration of concrements in the body, especially stones, using focused shock waves of high amplitude and steep rising edges. Normally, single pulses are directed to the concrement, wherein the first “half wave” corresponding to a compression dominates as regards edge steepness and amplitude whereas already the next succeeding half wave, corresponding to an expansion, is substantially less pronounced. Such pulses are used in a regularly repeated manner.
Comparable methods using shock waves are also known for other indications, e.g. for treating badly healing bone fractures.
The essential frequencies of the above-mentioned therapies are above the acoustic threshold; thus, these therapies are ultrasonic methods.
Although therapies using non-focused shock waves are known, the present invention is related to applications of focused waves (including pulses, compare above). Although the delimitation between focused and non-focused waves can be problematic, in the following, only such therapies shall be meant in which the shock waves are intentionally concentrated to a body region which is more or less extended in order to increase intensities, pressures or edge steepnesses.
Since in these focusing therapies the localization to the body region to be treated is essential, the adjustment of the respective apparatus for a correct positioning of the focus region in the body is of essential importance. This relates to a preliminary adjustment to the region to be treated, e.g. a stone, on the one hand. In case of too large tolerances, healthy tissue is damaged or unnecessarily much of healthy tissue is subjected to the therapy and, further, the success of therapy in the region to be treated is diminished or endangered. The term “navigation” is used here.
As a complication, further, the navigation does not necessarily need to be a static operation, i.e. changes during treatment may occur. Movements of the patient or displacements of organs, especially due to respiration, are an essential cause.
Image producing methods can be used for navigation that render the region to be treated distinguishable from surrounding regions and produce navigation information, i.e. coordinates, for the shock wave apparatus. Particularly known is a running X-ray monitoring during shock wave lithotripsy. Since at least two X-ray projections are necessary for the determination of the spatial position, a substantial technical effort for tilting X-ray axes and corresponding costs are caused. As regards the patient, X-ray monitoring leads to radiation exposure.